The present invention relates to an electrophotographic copying apparatus and more particularly, to an electrophotographic copying apparatus equipped with an improved scanning system control device which is arranged to control movement of the scanning system according to copy paper sizes or copying magnifications.
Commonly, in electrophotographic copying apparatuses of slit exposure type, it is so arranged that, while a photosensitive member or photoreceptor is moved at a predetermined speed, an optical system is also moved in synchronization therewith at a specific speed determined by the moving speed of the photoreceptor and copying magnification so as to optically scan an original to be copied for sequentially projecting light-wise images of the original onto the photoreceptor. It is to be noted that the "optical system" referred to hereinbelow means a fixed or stationary optical system associated with a movable original platform on which an original to be copied is placed in the case of a copying apparatus of movable original platform type, and a movable optical system including a light source, reflecting mirrors, etc. and moving under the lower surface of a fixed original platform in the case of a copying apparatus of movable optical system type.
In the copying apparatus of the latter type, i.e., of the movable optical system type as described above, if the moving distance of the optical system is arranged to be approximately equal to the length of the original to be scanned or that of the copy paper to be used so as to return the optical system immediately after completion of scanning, it is extremely advantageous from the viewpoint of practical use, since time and movement unnecessary for the copying operation are eliminated with consequent increase of the copying speed.
Conventionally, there has been proposed an arrangement as described above in which copy paper in the form of a roll is employed, with switch means or switch actuating member being arranged to be moved for cutting off the copy paper from the roll according to the length of the original to be copied, for example, in U.S. Pat. No. 3,751,158 wherein switch means for cutting the copy paper in the roll form and switch means for returning the optical system are movably disposed along the moving path of the scanning system, so that an operator actuates the switch means for cutting the copy paper into the length corresponding to the original, and also for returning the optical system.
However, for copying apparatuses in which copy paper sheets preliminarily cut into a predetermined length are employed, the known arrangement as described above in which the moving distance of the scanning system is controlled by the provision of the switch means and the like movable according to the length of the original, imposes, on the contrary, troublesome procedures on the part of the user, and moreover, is not preferable for the practical purpose, since the length of the copy paper does not necessarily correspond to that of the original. Accordingly, for the copying apparatuses employing cut copy paper sheets of predetermined size, there has been conventionally proposed an arrangement wherein the moving distance of the scanning system is preliminarily determined according to the kind of copy paper sheet employed, with switch means for returning purpose being disposed at a predetermined moving position so as to vary the moving distance of the scanning system through selective actuation of the switch means according to the sizes of the copy paper sheets, for example, in Japanese Laid Open Patent Application Tokkaisho No. 50/99152. The known arrangement as described above, however, still has disadvantages in that, if many kinds of copy paper sheets are employed, extremely complicated circuit constructions are inevitably involved in copy paper size selecting means and selecting means for the optical system returning switch, and the controlling is limited to two or three kinds of copy paper sheets at most, thus not being suitable for the practical purpose.
On the other hand, if the copying magnification varies with respect to the copy paper sheets of equal size, copying coverage i.e. area available for copying or area to be covered by copying on the original platform is altered. For example, when a reduced size copying or contraction is to be effected, the copying coverage becomes larger than the size of the copy paper sheet, while in an enlarge scale magnification copying or enlargement, the copying coverage becomes smaller than the size of the copy paper sheet. In other words, when the copy paper size and copying magnification are determined, the copying coverage or area available for the copying on the original platform is also determined, and if the scanning system as described above is moved at least by the amount equivalent to the area to be covered by the copying, the scanning movement suitable for the copy paper sheet size can be effected. However, it is not possible to effect controlling of the scanning system based on the conception as described above by switch means actuated merely through movement of the scanning system, and furthermore, even if the above control is intended to be achieved by setting of timer means, an extremely large number of timers are required or time set by the timers is not sufficiently accurate, and thus, almost no attention has been directed so far to the control of movement of the scanning system by the copy paper sizes and copying magnifications.